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Fetal Assessment and wellbeing in pregnancy (Fetal surveillance). BY DR ADDAH A.O.

Definition : fetal surveillance encompasses all measures taken in pregnancy to determine the well being of the fetus inutero up to delivery of the baby.

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Definition of terms.

Low birth wt – weighing less than 2500g at birth. Major cause of perinatal mortality. If identified in pregnancy need fetal surveillance.

Preterm infants – born before 37 weeks gestation. They are important contributor to LBW.

Small for gestational age (SGA) – Defined as bt wt (anthropometric measurement) less than 10th percentile of its specific GA. Some SGA infants may be constitutionally small and may represent only the tail end of normal distribution.

Intrauterine growth retardation – (IUGR)- A fetus is growth retarded when it fails to achieve its genetic potential. Such a fetus may still weigh 2500g or more and not fit in the category of SGA. High risk of perinatal mortality.

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Fetal surveillance in two parts,

Ante - partum fetal surveillance. Intra - partum fetal surveillance –uterine

contractions introduce a further risk of fetal hypoxia.

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Aim of fetal surveillance

To prevent fetal death or damage from chronic hypoxaemia.

To avoid unecessary intervention and so limit iatrogenic prematurity and unwanted operative delivery.

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Aetiology of fetal compromise.

The cause of stillbirth unknown in majority of cases. To mount a high level of fetal surveillance in all pregnancies to reduce neonatal morbidity/ mortality then becomes difficult,

A more practical step would be to identify the conditions which are associated with fetal growth restriction, fetal loss or damage and low birth wt (risk factors).

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Aetiology of fetal compromise contd. Identifying the mother at risk gives no

guarantee of success. A condition known to put the fetus at high risk may sometimes have no effect whatsoever while on the other hand some pregnancies with no perceived risk may be complicated by IUGR and even death. In view of this even the low risk mothers should have some level of surveillance.

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Risk factors for fetal compromise.

Maternal factors. Fetal factors. Placental factors. Environmental factors.

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Maternal factors.

Demographic factors Extreme of ages – less than 16 years and

over 40s. Nulliparity and grandmultiparity. Race .

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Maternal risk factors contd.

Medical condition. Factors that affect uteroplacental

circulation. Chronic hypertension. Early onset pre – eclampsia. Renal disease.

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Maternal risk factors continued

Maternal Hypoaxemia: severe Hypoxic conditions e.g chronic severe anaemia Chronic pulmonary disease. E.g bronchial

asthma. Cyanotic cardiac diseases.

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Maternal risk factors continue

Nutrition – severe maternal nutritional deprivation.

Maternal infections e.g malaria, toxoplasmosis. Also viral infection e.g CMV, varicella zoster, HIV infection.

Drugs – Alcohol, Cocaine, cigarette smoking

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Placental Factors

Abnormal Placental implantation.

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Environmental Factors

High altittude is associated with low birth weight

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Detecting the fetus at risk

To detect the high risk pregnancy from maternal risk factors, past obstetric history, as well as those risk factors developing during the pregnancy.

To implement appropriate antenatal care for high risk as well as the low risk pregnancy in order to detect fetal compromise.

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Detecting the fetus at risk contd.

Booking visit – Pregnancy dating (LMP) – decisions on

intervention require accurate knowledge of the gestational age of the pregnancy

Early ultrasound. Home based mothers records – A protocol

developed by obstetric units to identify high risk mothers.

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Detecting the fetus at risk contd. Continued antenatal care

Check maternal well-being and weight gain/attained weight in pregnancy.

Excluding infection such as malaria and UTI. Excluding severe anaemia Checking for fetal well-being indicated by fetal

movements over a period of time Symphysio fundal height measurements- single or

serial measurement may be needed to detect IUGR.

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Serial measurement of fetal growth Measurement of specific fetal sections on

ultrasound and compare it to the centile distribution for that gestation

Measurements of biparietal or head circumference to that of the abdominal circumference is used in the diagnosis of IUGR on ultralsound.

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Amniotic fluid volume (AFV)- In the absence of fetal anomaly and ruptured fetal membranes, AFV may give an indication of the extent of the fetal cardiovascular response to chronic hypoxic stress. Exact mechanism not known.

Fetal movement counting Not apparent to the mother until 16th to 20 weeks

gestation. There is a positive correlation between fetal movement and fetal health.

To monitor fetal movements several may be used but quite popular is the “Cardiff count to ten”. The woman is trained to record on a chart the time interval required to feel term fetal movement. The minimum number of fetal movement considered acceptable ranges from 3 – in one hour to ten – in 24hrs. The perception of less than 10 movements in 10hrs is an indication for NST.

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Fetal cardiotocography

NST- Does not require any external fetal or maternal

stimulation. Simply a continuous recording of fetal heart rate

and uterine contraction over a period of time usually 20 – 30 mins.

The rational behind this text is that it gives an indication via cerebrocardiac responses of fetal cerebral fetal activity which will become modified in the presence of fetal hypoxia.

The conclusion that can be drawn from the normal test is that at best the baby satisfactorily oxygenated at worst the level of hypoxia is not severe enough to produce brain dysfunction

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Criteria for a reactive or normal CTG – A normal base line heart rate of 110 - 150

beats per minute. A baseline variability of 5 – 25 beats/minute At least two accelerations of an amplitude of

10 – 15 beats minute over a period of 15 – 20 minute.

When CTG trace is abnormal other fetal assessment are carried out if time permits e.g fetal PH assessment before intervention.

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The contraction stress test

NST + Oxytocin Only practiced in the USA. It is invasive and time consuming.

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Fetal biophysical profile scoring

Attributes measures Fetal heart rate on CTG Fetal breathing movements Fetal tone Fetal body movements Amniotic fluid volume A score of 0 – 2 for each attributes given a

score of 10 as normal.

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Thank you!